Congress should override President Reagan's veto of the supplemental appropriations bill.

A vote to override would provide funds sorely needed for education and older- American programs, obviate any disruption in orderly public services and restore a sense of balance to the tattered relationship between the executive and legislative branches of our government.

Ironically, a vote to override also would help Reagan fulfill his commitments to friendly nations in the Western Hemisphere. It might be the one means of salvaging his Caribbean Basin Initiative.

Contrary to presidential rhetoric, this bill is not a "budget-buster." In aggregate, it appropriates almost $2 billion less than the president officially requested for the particular items the bill covers.

It is a bipartisan bill embraced by legislators of both political parties who clearly understand the need for its provisions. In the Senate, Majority Leader Howard Baker, Appropriations Committee Chairman Mark Hatfield and Budget Committee Chairman Pete Domenici all urged Mr. Reagan to sign the bill. Rep. Silvio Conte, ranking House Republican on the Appropriations Committee, made his plea quite public. Experienced Republican lawmakers tried to explain that the old, shopworn shibboleth of "budget-busting" simply would not wash in this case.

Members presumably voted their convictions when they passed the bill with only a handful of dissenters. If they vote their personal convictions on the veto, it will be overridden.

Congress did add some $917 million that the president had not requested for such things as elderly employment, student loans, education for the handicapped and advances to state unemployment funds. But we reduced other programs by $2.8 billion below their budgeted figures.

It is disappointing that the president used this supplemental bill as an excuse to renew his war against Congress -- and against the students, the handicapped and the elderly. If this veto is sustained, several hundred thousand young Americans will not be able to attend college this fall.

The veto and the president's shrill explanation for it are especially unfortunate following the conciliatory spirit that Congress exhibited on the tax bill last month, since they revive the spirit of confrontation and hostility that some of us had tried to put to rest.

What irony that only a week after the carefully choreographed embrace in the Rose Garden and Reagan's high-sounding appeal for a show of "unity," he went out of his way to pick an unnecessary fight with Congress!

Some contend that the veto was a sop to his party's right wing, disaffected by the tax increases that its members' own excessive tax cutting of last year made necessary. Others, groping for an explanation, hark back to this revelation contained in the Atlantic Monthly story on David Stockman:

"Disappointed by events and confronted with potential failure, the Reagan White House was developing a new political strategy: wage war with Congress over the budget issues, and in 1982 blame the Democrats for whatever goes wrong."

Whatever the reasoning, the political advisers who won out on this highly political veto have done the president a disservice. Reagan would have done better to follow the advice of Secretary of State George Shultz and Defense Secretary Caspar Weinberger, who urged that he sign the bill.

As one who has worked hard to build effective bipartisan backing for the president's Carribean Basin Initiative, I particularly regret the veto. I fear that it puts that program in jeopardy. Many of my colleagues are saying that if Reagan is unwilling to give needed help to the old, the poor and the handicapped in our own country, he scarcely can expect Congress to appropriate more money for such people in other countries.

If our hemispheric program should fall victim to a wounded sense of priorities and to the polarization exacerbated by this highly political veto, then that could be the greatest tragedy of all. Our friends in Latin America will not understand the political nuances. They will understand only that the United States went back on its word. For all of these reasons the president, the Congress and the nation will be better served if the veto is overridden.